Persistent pain is a major challenge for patients who undergo hematopoietic stem cell transplant (HSCT) and is related to more fatigue, more physical disability, poorer quality of life, and poorer medical adherence. There is a need to examine strategies for managing pain in HSCT patients that can complement existing analgesic regimens. Strong evidence suggests that cognitive and behavioral factors play an important role in HSCT patients' ability to manage their pain. We have found that HSCT patients having low levels of confidence (i.e., self-efficacy) in their ability to control pain and high use of maladapive coping strategies (i.e., pain catastrophizing) experience increased pain and disability. A psychosocial intervention that modifies patients' cognitive and behavioral pain coping strategies may benefit HSCT patients. Protocols, particularly Pain Coping Skills Training (PCST), have been developed for reducing pain and improving quality of life in patients with persistent pain. However, HSCT patients with persistent pain face a number of unique challenges that must be considered when applying a PCST protocol. We propose to develop and test a Mobile Health Pain Coping Skills (mPCST) protocol for HSCT patients with persistent pain to meet the challenges of HSCT patients with pain as they transition from hospital based care to their home environment. The first aim of this study is to use an iterative development model to design a mPCST intervention protocol for HSCT patients that targets increasing self-efficacy for pain control and decreasing pain catastrophizing. We will use focus groups with patients and HSCT providers to guide development along with user testing with HSCT patients having pain. The second aim of this study is to use a small randomized controlled trial to examine the feasibility, acceptability, and engagement in the developed mPCST protocol. The third aim is to obtain an estimate of the effect size of the developed mPCST protocol on decreased pain, pain disability, physical disability, and adherence to post-transplant lifestyle recommendations impacted by pain when compared to a standard care control condition. Proposed innovative features of the mPCST protocol that will be developed include: extensive input from PCST and HSCT experts and HSCT patients with pain; an initial session prior to discharge with subsequent sessions occurring at home via video-conferencing; incorporation of strategies to decrease the impact of pain on adherence to critical post-transplant lifestyle recommendations; a real-time daily assessment system with subsequent tailored feedback. If the developed mPCST protocol demonstrates feasibility, acceptability, engagement, and promising effect sizes to influence pain and other indices of quality of life, a larger NIH grant wll be sought to examine this protocol in a larger sample of patients, test the protocol against an active treatment, and investigate a broader array of outcomes (e.g., medication adherence). This mPCST protocol could also be examined in other patient populations with pain facing similar challenges (e.g., live far from medical center, travel limitations).